Device for determining a parasitic resistance in video endoscopes

The present application is a continuation of PCT/EP2020/052570 filed on Feb. 3, 2020, which is based upon and claims the benefit to DE 10 2019 103 287.3 filed on Feb. 11, 2019, the entire contents of each of which are incorporated herein by reference.

The present disclosure relates to video endoscopes and more particularly to a device for determining a parasitic resistance of an electronic circuit for a video endoscope, comprising a potential-determining conductor which is connected to a potential-determining device, wherein the potential-determining conductor is situated on a printed circuit board.

The functioning of electronic circuits in video endoscopes can be influenced by parasitic resistances. A parasitic resistance is an unreliable resistance between two independent signals or levels or conductors of an electronic circuit. There are electronic circuits that are sensitive to faults of this kind, for example analog-digital converters (ADC) or comparators, which are operated by means of high-ohmic voltage dividers or high-resistance voltage dividers. Parasitic resistances can occur during operation of endoscopes, such as in video endoscopes, for example if the video endoscope comes into contact with conductive particles or moisture or if there is an ingress of water. Typically, video endoscopes have a hermetic space, in which optical systems are arranged, for example, and a non-hermetic space, which is provided in a handle, for example. During autoclaving of video endoscopes, it is possible, for example, for moisture to enter the handle and thus cause problems with parasitic resistances.

An object is to provide a device for determining a parasitic resistance of an electronic circuit for a video endoscope that enables reliable determination of a parasitic resistance and that is as cost-effective as possible, for example through the use of only a few or no additional components of the electronic circuit.

Such object can be achieved by a device for determining a parasitic resistance of an electronic circuit for a video endoscope, comprising a potential-determining conductor which is connected to a potential-determining device, wherein the potential-determining conductor is situated on a printed circuit board, wherein the potential-determining conductor is arranged along a path on the printed circuit board next to a reference potential conductor, wherein a parasitic resistance can be determined between the potential-determining conductor and the reference potential conductor.

By providing the device, it is possible to reliably and accurately determine a parasitic resistance between the potential-determining conductor and the reference potential conductor, such as by the potential-determining device. As a result, in the regions of the printed circuit board in which both a reference potential conductor and a potential-determining conductor are provided, it can be reliably determined whether parasitic resistances are present, for example on account of moisture. If multiple potential-determining conductors are provided which are arranged in different regions of the printed circuit board or in different sections of the printed circuit board, and next to a reference potential conductor in each case, wherein said reference potential conductor has or may have the same reference potential, it is even possible to establish the region of the printed circuit board in which parasitic resistances are present.

The parasitic resistance can be determined during operation or during start-up of the electronic circuit of the video endoscope, i.e., during operation or during start-up of the video endoscope.

A path on the printed circuit board can be understood to mean a spatial extent or a portion or region of the printed circuit board that is elongated. The path can be a longitudinal extent of the printed circuit board.

The length of the path can be at least one quarter, such as, at least one half of an extent of the printed circuit board. As a result, it can be determined over a large region of the printed circuit board whether a parasitic resistance is present. An integral can be formed over various parasitic resistances as a result. The length of the path can be greater than or equal to ⅔ or greater than or equal to ¾ or greater than or equal to 1.25 or greater than or equal to 1.5 times the extent of the printed circuit board, such as in the longitudinal extension of the printed circuit board. The length of the path can be less than 100 times, such as, less than 50 times, less than 20 times, less than 10 times the size of the longitudinal extent of the printed circuit board.

The potential-determining conductor can be arranged on the printed circuit board in a meandering pattern.

The distance between the potential-determining conductor and the reference potential conductor in the regions in which these are arranged one next to the other can be substantially the same. As a result, the parasitic resistance can be determined very accurately. If the distance between the potential-determining conductor and the reference potential conductor in the region in which these are arranged one next to the other is less than or equal to one half, such as one quarter of the distance from the potential-determining conductor to another conductor that has a different potential to the reference potential conductor, the parasitic resistance can be effectively prevented from being compensated by a parasitic resistance between the potential-determining conductor and said other conductor. The other conductor can be the conductor that is closest to the potential-determining conductor after the reference potential conductor, which is closer to the potential-determining conductor.

The ratio of the distance between the potential-determining conductor and the reference potential conductor to the distance between the potential-determining conductor and the other conductor can be ⅓, ¼, ⅕, 1/10 or even smaller.

The distance can be determined perpendicularly to the potential-determining conductor.

The potential-determining conductor can be surrounded on at least two sides by the reference potential conductor. This makes the result even more accurate.

The potential-determining device can be an analog-digital converter or can comprise an analog-digital converter, wherein the analog-digital converter can be provided in a microcontroller or as an alternative function in a microcontroller, wherein the microcontroller can be a microcontroller that is provided for an electronic circuit for a video endoscope and that performs at least one other function of the electronic circuit of the video endoscope.

Said other function of the electronic circuit may be actuation or control of an image-capturing device.

An analog-digital converter provided in the potential-determining device converts an analog voltage Vin (voltage to be measured) into a digital value um. For example, a piece of software compares the digital value with a limit value in order to make a true-false decision. For example, “true” may be provided when the measured value is greater than the limit value and “false” when the measured value is less than or equal to the limit value. Depending on the measuring circuit used, this makes it easy to identify a parasitic resistance.

The potential-determining device may also be configured to be analog.

4 5 FIGS.and As an alternative to the analog-digital converter, a comparator circuit may be used. In this case, no analog-digital conversion and no software are required. The comparator circuit compares the voltage to be measured or input voltage Vin with a reference voltage Vref (see). At the output of this circuit, an item of true-false information can be picked off from the output signal based on a HIGH or LOW level. The output voltage Vout is for example “HIGH” when the input voltage is greater than the reference voltage and the output voltage is for example “LOW” when the input voltage is less than or equal to the reference voltage. If the limit value has to be changed, only the reference voltage needs to be changed. A hysteresis can be provided in order to enable stable functioning of the comparator.

The potential-determining conductor can be connected to a voltage divider. For this purpose, the potential-determining conductor runs between two resistors of the voltage divider, such that the potential-determining conductor has a precisely predefined potential if no parasitic resistance is present. In the case where a parasitic resistance is present, the magnitude of the parasitic resistance can be easily determined via the measured potential at the potential-determining conductor.

Alternatively, the potential-determining conductor can be provided between a pull-up resistor and ground, wherein the parasitic resistance can be determined between the potential-determining conductor and ground. As a result, it is possible to determine parasitic resistances without additional electronic components of the electronic circuit for a video endoscope.

The potential-determining conductor can be provided between a pull-down resistor and a reference potential conductor, wherein the parasitic resistance can be determined between the potential-determining conductor and the reference potential conductor. This therefore also makes it possible to determine parasitic resistances without additional electronic components of the electronic circuit for a video endoscope.

An electronic circuit for a video endoscope can be provided with a device of the like described above.

Furthermore, a video endoscope can be provided with the electronic circuit described above.

If the device is arranged in a non-hermetic space of the video endoscope, such as at least in part in a handle of the video endoscope, possible parasitic resistances can be determined very efficiently.

In the drawings, the same or similar elements and/or parts are, in each case, provided with the same reference numerals such that they are not introduced again in each case.

1 FIG. 10 11 21 13 13 12 24 12 22 1 2 12 22 1 2 16 22 schematically shows a circuit diagram of a device for determining a parasitic resistanceof an electronic circuitfor a video endoscope. A microcontrollerhaving an analog-digital converter, or AD converter, is provided. The input of the AD converteris connected to a potential-determining conductor, to which a potential that corresponds to a voltageto be measured is applied. The potential-determining conductoris connected to a voltage divider, which comprises two resistors R, R. The potential-determining conductoris connected to the voltage dividerbetween these two resistors R, R. A reference potential conductorhaving a potential of, by way of example, 3.3 volts is provided. The voltage dividerhas 3.3 volts on one side and is connected to ground GND on the other side.

10 12 16 24 10 10 1 22 10 In the presence of a parasitic resistancebetween the potential-determining conductorand the reference potential conductor, the voltageto be measured is different than in the absence of a parasitic resistance. The parasitic resistoris connected in parallel to the resistor Rof the voltage divider, such that the parasitic resistancecan easily be determined.

2 FIG. 10 11 10 21 21 schematically shows a circuit diagram of another embodiment of a device for determining a parasitic resistanceof an electronic circuitfor a video endoscope. In this case, the parasitic resistanceis determined functionally such that no additional components are required per se for the electronic circuit, which is provided for a video endoscope. For this purpose, an output of the microcontrolleris used as a switching output as opposed to an analog-digital converter after start-up of the microcontroller.

21 12 25 3 10 21 25 21 23 12 2 FIG. 2 FIG. When the microcontrollerhas been started up, the potential determining conductorserves as a switching signal in that the switch, which switches a load resistor Rto 18 volts, is used to determine parasitic resistanceswhen the microcontrolleris being started up. During start-up, the switchis open and the output of the microcontrollercan be used as an analog-digital converter if a pull-up resistoris provided as in. For the case shown in, the potential-determining conductoris arranged opposite ground or along a certain path with a ground conductor as the reference potential conductor.

23 10 12 2 FIG. For the case not shown, in which a pull-down resistor is provided, i.e., for the case in which the resistorsandare swapped with respect to, the potential-determining conductorwould, in this example, be arranged on a path of the printed circuit board next to a potential of 3.3 volts provided as the reference potential conductor.

3 FIG. 10 12 14 13 15 18 22 schematically shows a printed circuit board of an electronic circuit on which a device for determining a parasitic resistanceis arranged. Some conductor tracks are shown, the function of which is not specified here. The potential-determining conductorruns from the top-right region from a contactfor the potential-determining deviceover a relatively long path in the longitudinal extension of the printed circuit boardto a contactfor the voltage divider.

12 16 1 1 10 1 12 16 15 The potential-determining conductoris arranged substantially in parallel next to the reference potential conductorover the longest part of the path and said conductors are arranged at a short distance dfrom one another. The distance dis the same size everywhere, if possible. A parasitic resistancecan be measured over this distance d. In this exemplary embodiment, the reference potential is, by way of example, 3.3 volts. The path in which the potential-determining conductorand the reference potential conductorare arranged in parallel or next to one another can be seen to correspond to almost 1.5 times the longitudinal extent of the printed circuit board. As a result, a parasitic resistance can be determined very accurately.

2 12 20 16 10 15 17 3 FIG. It is also important that the distance dfrom the potential-determining conductorto the next conductorhaving another potential, for example ground GND, is significantly greater than the distance to the reference potential conductor. This causes fewer measurement errors during determination of the parasitic resistance. The longitudinal extent of the printed circuit boardis shown by the reference numberin.

4 FIG. 1 2 FIGS.and 30 30 31 32 13 is a schematic circuit diagram of a comparator. An input voltage Vin is applied to an input of a differential amplifier. The reference voltage Vref is applied to the other input of the differential amplifier. The comparator is supplied with a supply voltage Vdd. In addition, the reference voltage Vref is between two resistorsand, which are between the reference voltage Vdd and ground, i.e., GND or 0 volts. The configuration of a comparator, which is common per se, can be used instead of the analog-digital converter, namely as the potential-determining devicein.

5 FIG. shows voltage curves over time. When the input voltage Vin is less than or equal to the reference voltage, the output signal is LOW. When the input voltage is greater than the reference voltage, the output signal Vout is HIGH.

In order to prevent the comparator from switching over too frequently and irregularly on account of minor fluctuations of the input voltage or reference voltage, the comparator can be provided with a hysteresis and configured as a Schmitt trigger.

In this way, the potential-determining device can be analog in configuration.

While there has been shown and described what is considered to be particular embodiments, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.

10 Parasitic resistance or resistor 11 11 ,′ Electronic circuit 12 Potential-determining conductor 13 Potential-determining device 14 Contact for potential-determining device 15 Printed circuit board 16 Reference potential conductor 17 Printed circuit board extent 18 Contact for voltage divider 20 Conductor 21 Microcontroller 22 Voltage divider 23 Pull-up resistor 24 Voltage to be measured 25 Switch 30 Differential amplifier 31 32 ,Resistor 1 dDistance 2 dDistance GND Ground 1 2 3 R, R, RResistor Vin Input voltage Vref Reference voltage Vout Output voltage Vdd Supply voltage